WO94/22296 discloses a horse shoe of the type mentioned by way of introduction. A horse shoe of this type enjoys major advantages in that it effectively damps impact and jolts against the hoof, in particular if the horse is running on hard ground.
FIGS. 1, 2 and 3 show the prior art horse shoe. It will be particularly apparent from FIG. 2 that the outer side of the prior art horse shoe is substantially smooth and approximately at right angles to the plane of the horse shoe when the horse shoe is not under loading. FIG. 3 shows the same cross section in which, however, the section has been greatly deformed in that the rubber material has been compressed such that the outer side of the shoe inclines, in a downward direction, manifestly outwards from the centre point for the shoe.
In particular in cold weather, typically temperatures lower than -5.degree. C., cracks occur in the prior art horse shoe, in particular in the region of the nail holes and out towards the outside of the shoe. If unevenness in the ground comes into contact with the deformed shoe, particularly the edge region at the outside of the shoe where the rubber material is under great stress, cracks readily occur in the material. Such loadings may even be so great that whole pieces of the rubber material are broken off.
At higher temperatures, this problem is less severe, since the movements in the rubber material will be more uniformly distributed throughout its entire volume.
Because the rubber is visco-elastic, a horse shoe of the type under consideration here shows a tendency to undergo plastic alterations after a period of use. Such plastic alterations deform the cross section of the horse shoe from the appearance illustrated in FIG. 2 in direction towards (or even beyond) the appearance illustrated in FIG. 3, such that, after a period of use and under loading, the horse shoe may become considerably wider at its lower edge than is the case at its upper side. If a deformed horse shoe in accordance with the foregoing is subjected to loading against an uneven substrate, the deformation will naturally be even greater locally, whereby very large local stress peaks occur such that the problem is aggravated.
Those areas of the prior art horse shoe which are particularly vulnerable are the areas surrounding the nail holes.